Top-loading balance

ABSTRACT

The parallelogram linkage of a top-loading balance which maintains the positions of the weighing pan parallel during pivoting movement of the balance beam includes the beam, a portion of the stationary support structure, and two guide members, which are connected by band hinges. The major dimensions of each band in the two hinges on the ends of the guide member parallel to the balance beam are located in one of two intersecting planes in a certain angular position of the guide member and the connected other linkage member. Only the major dimensions of one band are located in one of the planes, thereby reducing the torsional stiffness of the parallelogram linkage and minimizing the effect of the linkage on the weight response of the balance.

1 51 Jan. 9, 1973 1541 TOP-LOADING BALANCE Max K. A ppius, Berneck,Switzer- [75] Inventor:

- land [73] Assignee: Mettler Instrumente AG, Griefensee-Zurich,Switzerland 221 Filed: May28,l971

211 Appl.N0.: 147,803

[30] Foreign Application Priority Data June l, 1970 Switzerland..8185/70 [56] References Cited UNITED STATES PATENTS 2,939,694 6/l960Bradley ..177/1)1G. 9 392,617 11/1888 1.161) et al ..177/1)1o. 93,l48,742 9/1964 0111116 177/010. 9

Primary ExaminerGeorge H. Miller, Jr. Attorney-Kelman and Herman [57]ABSTRACT The parallelogram linkage of a top-loading balance whichmaintains the positions of the weighing pan parallel during pivotingmovement of the balance beam includes the beam, a portion of thestationary support structure, and two guide members, which are connectedby band hinges. The major dimensions of each band in the two hinges onthe ends of the guide member parallel to the balance beam are located inone of two intersecting planes in a certain angular position of theguide member and the connected other linkage member. Only the majordimensions of one band are located in one of the planes, therebyreducing the torsional stiffness of the parallelogram linkage andminimizing the effect of the linkage on the weight response of thebalance.

7 Claims, 5 Drawing Figures PATENTEUJAN 9 197a FIG.I

l l\ 3b e 7 PI FlG. 2

FIG.3

I INVENTOR. MAX K. APPI US BY M AGENTS TOP-LOADING BALANCE Thisinvention relates to top-loading balances, and particularly to animproved guide system for holding the loading face of the weighing panin such a balance in positions parallel to each other during movement ofthe balance beam.

It has been proposed heretofore to employ elastic ribbon bearings inbalances in which the weighing 'pan is suspended from the beam by meansof a hanger. An elastic ribbon bearing maybe used as the main bearingconnecting the beam to the normally stationary support structure of thebalance, and another elastic ribbon bearing may connect the hanger ofthe weighing pan to the beam. Each bearing includes two flexible ribbonsor bands of spring-temper metal whose terminal portions are fixedlyfastened .to the connected balance elements in such a manner that theribbons intersect each other. The bearing axis is located in the line ofintersection of the two planes defined by the ribbons in a certainangular position of the two connected elements.

The ribbon bearings of the type described above have advantages overbearings employing a knife edge and a plate in that they are not subjectto wear. Yet, they were not employed heretofore in the guide system of atop-loading balance which maintains the horizontal position ofthe-weighing pan, and more particularly of its upwardly directed loadingface. A parallelogram linkage is the basic feature of the guide system,and it is practically impossible to maintain precise parallel alignmentof the pivot axes in the four corners of the parallelogram when thelinkage members are con- FIGS. 2 to 5 illustrate the balance of FIG. '1in respective fragmentare sections on the lines Il-Il, III-- III, lV-IV,and V-V.

Thenormally stationary supporting structure of the illustrated balanceconsists of two columns 1 integrally cast with a common base plate andupright in the illustrated operative position of the balance. The topends of the columns 1 are fixedly connected by a cross bar 2 of squarecross section, and another cross bar 19 vertically aligned with the bar2 connects the columns 1 near their common base plate. The diagonalplanes of the bars 2, 19 are vertical and horizontal, and all othercross bars referred to hereinbelow are of square cross section andsimilarly oriented when in the illustrated position.

A movable cross bar 4 is suspended from the parallel cross bar 2 bymeans of a flexible band hinge essentially consisting of two pairs 3a,3b of thin, spring-temper metal bands. In the illustrated position ofthe ap- I paratus, the major dimensions, that is, the length and widthof each band are locatedin two planes intersecting each other in ahorizontal line parallel to'the elon- I gation's of the bars 2, 4. Thebar 4 may pivot on the bar 2 about an axis coinciding with the line ofintersection.

The beam 5 of the balance is received in a notch of the cross bar 4 andfixedly fastened to the bar 4 so that the afore-described band hingeconstitutes the'main bearing of the balance. The longer arm 5b of thebeam nected by hinges corresponding to the known elastic ribbonbearings. Contrary to knife edge bearings, rib

bon bearings cannot be adjusted after installation. Even slightmisalignment of the hinge axes would affect the response of the balanceto an applied load, particularly the change in the angular position ofthe balance beam under increasing load. I I

.The primary object of the invention is'the provision of an'improvedhinge arrangement for a parallelogram linkage of the type described inwhich the linkage and its elements do not affectthe response ofthebalance beam to an applied load. It is another object to provide aguide system for the weighing pan ofa balance which prevents erroneousreadings when the notcentrally loaded.

According to the invention, these objects are achieved by the use offlexible band hinges on a guide member of the parallelogram linkagewhich is parallel to the balance beam. As is known in itself, the majordimensions, that is, length and width, of each band are located in oneof two intersecting planes in a certain angular position of -theparallelguidemember and a connected member, but the major dimensions of only oneband are located in one of the planes.'The torsional stiffnes's'of thehingeis greatly reduced by'such an arrangement, and misalignment of thehinge axes in the FIG. 1 shows atop-loading balance of the invention inside-elevational section on the line [-1 in FIG. 2;

weighing pan is 5 carries a plate 6 whose vertical face is provided withan arcuate row of indicia centered in,the axis of the band hinge 3a, 3b.The optical system employed for projecting the indicia on a ground glasscarrying a reference line has been omitted since it may be entirelyconventional. The longer arm 5b of the beam 5 also carries acounterpoise 7.

The shorter arm 5a of the beam 5 which extends obliquely upward from themain bearing is. fixedly fastened to a horizontal cross bar 8, andanother horizontal cross bar 10 is attached to the bar 8 by pairs 9a,9b. of flexible metal bands in a hinge arrangement virtually'identicalwith that forming the main bearing of the balance. A flat guide bar 11is fixedly attached to the cross bar 10 and projects upwardly beyond thehingedly connected cross bars 8, l0 and the beam 5. ,Its upper endcarries a fixedly fastened weighing pan 12 having a top face which ishorizontal when the balance base is similarly oriented. The load to beweighed acts on the top face of the pan 12 as indicated by an arrow P.

The lower end of the guide bar 11 carries a horizontal cross bar 13connected by two spring-metal bands 14a,- 14b with a cross bar 15 on oneend of another guide bar 16. The other end of the bar 16 is hingedlysecured to the afore-mentioned cross bar 19 by a much shorter cross bar17 fixed on the bar 16 and by three metal bands 18a, 18b, and 181)".

As is best seen in FIG. 4, the bars 13, 15 are connected'by only twometal bands 14a, 14b which are located on either side of the guide bar16, and whose effective width in the direction of the hinge axis isreduced by slots 20 elongated in a direction from the terminal portionof each band 14a, 14b fastened to the cross bar 13 toward the terminalportion fastened to the cross bar 15. The short screws which hold thebands 14a, 14b to the associated cross bars have been omitted from FIG.4 for the sake of clarity, and corresponding screws have been omittedfrom FIGS. 2 3, and 5. When the hinge of FIG. 4 is viewed in FIG. 1, itis seen that the width and length of only the one band 14a extends inthe plane which is perpendicular to the plane defined by the width andlength of the band 14b. The minimum number of resilient bands togetherwith the slots 20 reduces the torsional stiffness of the hingedconnection between the guide bars 11, 16 sufficiently to compensate formisalignment in the parallelogram linkage constituted by the guide bars11, 16 for the pan 12, the shorter arm 5a of the beam 5, and the part ofthe support structure 1 between the bars 2 and 19.

The hinge connection between the bars 17, 19 is only I slightly stifferin torsion than that described with reference to FIG. 4. As is evidentfrom joint consideration of FIGS. 1 and 5, the length and width of onlya single band 180 are located in the plane extending from the upperright to the lower left in FIG; 1, and the two bands 18b and 18b" whichare'located in the other plane and are symmetrical'relative to the band18a in the view of FIG. 5 have a combined width. in the direction of thehinge axis which is not greater than the corresponding dimension of theband 18a. The'hinge arrangement of FIG. 5 thus also has limitedtorsional stiffness in the plane of FIG. 5.

Because of their low torsional stiffness in the vertical planes of FIGS.4 and 5, the two hinge arrangements on the guide bar 16 do not affectthe response of the beam 5 to a load P applied to the weighing pan 12 inany angular operative position of the beam, and the four hinge axes arealigned automatically.- The hinges at the ends of the guide bar 16 haverelatively high flexural stiffness in respective horizontal planesthrough their pivot axes, and thereby prevent incorrect readings on thebeam 5 when an applied load is not centeredon the loading face of thepan 12. The parallelogram guiding system constituted by the guide bars11, 16, the beam 5, and the support 1 is virtually free from lostmotion.

While it is preferred to employ elastic band hinges at all four cornersof the parallelogram, many of the advantages of the invention areretained if the hinges connecting the balance beam 5 to other members ofthe parallelogram linkage are of a different type, for example, of theknife edge and plate type.

It should be understood, therefore that the foregoing disclosure relatesonly to preferred embodiments of the invention, and that it is intendedto cover all changes and modifications of the example of the inventionherein chosen for the purpose of the disclosure which.

do not constitute departures from the spirit and scope of the inventionset forth in the appended claims.

What is claimed is: l. A balance comprising, in combination: a. anormally stationary support; b. a beam; 7 c. pivot means securing saidbeam to said support for pivoting movement about a pivot axis,

1. said beam having two arms extending from said pivot means in oppositedirections; d. first and second guide members; e. first, second, andthird hinge means having respective first, second, and third hinge axesat least approximately parallel to said pivot axis,

1. said first hinge means hingedly securing said first guide member tosaid support,

2. said second hinge means hingedly securing said second guide member tosaid first guidemember, and

3. said third hinge means hingedly securing said second guide member "toone of said arms in a position in which said one arm, said support, andsaid guide members jointly constitute a parallelo'gra'm linkage,

4. said support and said second guide member being upright in all normaloperating positions of said balance; I

f. a weighing pan mounted on said second guide member,

1. said pan having a loading face located above said beam and upwardlydirected in said operating positions;

g. a counterpoise on the other arm of said beam; and Y 3. A balance asset forth in claim 2, wherein said first and second hinge means eachinclude a plurality of flexible band members securing said first guidemember to other members of said linkage, each band member having twoterminal portions fastened to said guide member and to an associatedother member of said linkage respectively, and having two majordimensions of length and width substantially greater than the thicknessof said band member, in a predetermined angular position of said guidemember and said associated other member, the major dimensions of eachband member extending in one of two planes intersecting each other, themajor dimensions of not more than one band member extending in oneofsaid planes.

4. A balance as set forth in claim 3, the major dimensions of at leasttwo of said band members in said first hinge means extending in theother plane in said predetermined angular position.

5. A balance as set forth in claim 3, one of the band members of saidsecond hinge means being formed with slots elongated in a direction fromone of said terminal portions to the other terminal portion, said slotsbeing of a number and of a size sufficient to significantly decrease thetorsional stiffness of said second hinge means.

6. A balance as set forthin claim 3, said third hinge means and saidpivot means each including a plurality of flexible band members, theband members of said third hinge means having each two terminal portionsfastened to said beam and to said second guide member respectively andhaving two major dimensions of length and width, said major dimensionsof each band member of the third hinge means extending in one of twoplanes intersecting each other substantially in the hinge axis of saidthird hinge means, the band members of said pivot means having each twoterminal portions fastened to said beam and to said support respectivelyand having each other substantially in the hinge axis of said thirdhinge means, and the major dimensions of two flexible band members ofsaid pivot means extending in each of the two planes intersecting eachother substantially in said pivot axis.

1. A balance comprising, in combination: a. a normally stationarysupport; b. a beam; c. pivot means securing said beam to said supportfor pivoting movement about a pivot axis,
 1. said beam having two armsextending from said pivot means in opposite directions; d. first andsecond guide members; e. first, second, and third hinge means havingrespective first, second, and third hinge axes at least approximatelyparallel to said pivot axis,
 1. said first hinge means hingedly securingsaid first guide member to said support,
 2. said second hinge meanshingedly securing said second guide member to said first guide member,and
 3. said third hinge means hingedly securing said second guide memberto one of said arms in a position in which said one arm, said support,and said guide members jointly constitute a parallelogram linkage, 4.said support and said second guide member being upright in all normaloperating positions of said balance; f. a weighiNg pan mounted on saidsecond guide member,
 1. said pan having a loading face located abovesaid beam and upwardly directed in said operating positions; g. acounterpoise on the other arm of said beam; and h. indicia means on saidparallelogram linkage for indicating the angular position of said beamrelative to said pivot axis,
 1. the respective torsional stiffnesses ofsaid pivot means transverse to said pivot axis and of said third hingemeans transverse to said third hinge axis being substantially greaterthan the respective torsional stiffnesses of said first and second hingemeans transverse to said first and second hinge axes.
 2. said secondhinge means hingedly securing said second guide member to said firstguide member, and
 2. A balance as set forth in claim 1, wherein saidindicia means are mounted on said beam.
 3. A balance as set forth inclaim 2, wherein said first and second hinge means each include aplurality of flexible band members securing said first guide member toother members of said linkage, each band member having two terminalportions fastened to said guide member and to an associated other memberof said linkage respectively, and having two major dimensions of lengthand width substantially greater than the thickness of said band member,in a predetermined angular position of said guide member and saidassociated other member, the major dimensions of each band memberextending in one of two planes intersecting each other, the majordimensions of not more than one band member extending in one of saidplanes.
 3. said third hinge means hingedly securing said second guidemember to one of said arms in a position in which said one arm, saidsupport, and said guide members jointly constitute a parallelogramlinkage,
 4. said support and said second guide member being upright inall normal operating positions of said balance; f. a weighiNg panmounted on said second guide member,
 4. A balance as set forth in claim3, the major dimensions of at least two of said band members in saidfirst hinge means extending in the other plane in said predeterminedangular position.
 5. A balance as set forth in claim 3, one of the bandmembers of said second hinge means being formed with slots elongated ina direction from one of said terminal portions to the other terminalportion, said slots being of a number and of a size sufficient tosignificantly decrease the torsional stiffness of said second hingemeans.
 6. A balance as set forth in claim 3, said third hinge means andsaid pivot means each including a plurality of flexible band members,the band members of said third hinge means having each two terminalportions fastened to said beam and to said second guide memberrespectively and having two major dimensions of length and width, saidmajor dimensions of each band member of the third hinge means extendingin one of two planes intersecting each other substantially in the hingeaxis of said third hinge means, the band members of said pivot meanshaving each two terminal portions fastened to said beam and to saidsupport respectively and having two major dimensions of length andwidth, said major dimensions of each band member of said pivot meansextending in one of two planes intersecting each other substantially insaid pivot axis.
 7. A balance as set forth in claim 6, the majordimensions of two flexible band members of said third hinge meansextending in each of the two planes intersecting each othersubstantially in the hinge axis of said third hinge means, and the majordimensions of two flexible band members of said pivot means extending ineach of the two planes intersecting each other substantially in saidpivot axis.